I asked the question about how long before I change from my screen filter to paper filter and was told that the screen filter could be left in there forever and just keep cleaning it. I plan on keeping the screened filter in until I get no more metal shavings then I will go to paper filters. I was told that others have seen metal in the screen for about a thousand miles or less. Hope that helps. I should have added that I will get rid of the screen filters when I stop seeing bigger flakes in the oil.